Range finder



June 4, 1946. B. E. LUBoSHEz 2,401,688

RANGE FINDER Filed July 18, i941 8 Sheets-Sheet- 1 97 L56 3 l f Benjamin E.Luboshez 95E BY 3 ATTORNEY June 4, 1946. B E, LUBOSHEZ 2,401,688

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ubos hez IN VEN TOR A TTORNEY Benjamin E. L

June 4, 1946. E, E LUBOSHEZ 2,401,688

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Benjamn E. Luboshez v f INVENTOR BY WW A TTQRNE Y June 4, 1946.

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' RANGE FINDER Filed Ju1y 18, 1941 a sheets-sheet s Benjamin E.Lub0shez INVENTOR A TTORNE Y June 4, 1946. B. E. LuBosHEZ 2,401,688'

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mmm. Mmm N EN EN ABerg/'01min E.Lub0sz y INVENTOR BY ATTORNEY Patented June 4, 1946 RANGE FINDER `Benjamin E. Luboshez, Rochester, N. Y., asslgnor toAEastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application July 18, 1941, Serial No. 402,982

This invention relates to range finders. i

Various forms of this invention are described in my copending application Serial Numbers 402,- 983, 402,984, 402,985, and.402,986, all filed concurrently herewith.

It isthe primary'object of this invention to provide a method of range finding and a range finder which is more accurate than previous systems, which is independentv of the observers ability to judge stereo effects and which works equally well with sharp and diffused objects.

A review of prior range finding systems indicates that they can be dividedinto two general classes. The flrst of these, namely the coinci.

dent type may have various forms, for example, the overlapping image type whose accuracy is inferior to the other types. the split-field type,

which is probably the most' accurate of all but requires well-defined properly placed sharp lines in the target for maximum accuracyand thirdly,

the unequal magnification type in which the 3'1 claims. (Cms- 2.7)

2 accompanied by image rotation and blurring. Thus there was no viewpoint motion along a path as in my preferred system nor was there any coupled mirror systems as employed in the various forms of my range finder.

Accordingto the invention, there is provided a new lmethod etrange finding which consists in forming an image of the object whose range is to be found by means .of an objective, then shifting the effective view point of the objective such as along a repetitive path relative to the focus plane of the objective. If an eye-piece is used, this focus plane is also the focus plane of the eye-piece. This shifting of the view point of the objective which may be accomplished in numerous ways described later, causes the image to shift similarly relative to the optic axis.4 If some :means of arresting this motion of the image is provided,

adjacent to each mark, or` with a wandering mark l whose adjustment may be read against a suitable scale.

' Thus the accuracy of all prior range nfinders depends in the limit upon one of two factors. Either the accuracy in which coincidence can be detected or the lprecision with which differences in depth in stereoscopic Vvision can be perceived.

The present invention, on the other hand, involves an entirely new principle and depends for its accuracy on the sensitivity of the eye to the perception of movement. It iswell known that the eye is very quick to perceive that movement is taking place evenif the moving object be very ill-defined. Thus the principle of the present invention does not have the inherent disadvantage of al1 coincident types for which well defined targets are so essential.

One interesting prior system attempted to get a stereo effect by having an obliquely oriented mirror rotating intermittently in front of a telescope and about the optic axis thereof. A series of radially located fixed mirrors provided a series of fixed but different viewpoints for the objective. Continuous motion was impossible since an optical sweeping of the xed mirrors would be while continuing the shifting of the viewpoint,

the range of the object is found by noting the ady justment of the image motion control device necessary to stop the image motion. For example, if the viewpoint of the objective is moved in a circular path, the corresponding circular motion of the image depends on the distance of the object vfinding may be performed, consists of an objective for forming in its focus plane an image of the object whose range is to be found and some means for shifting the effective viewpoint of the objective while keeping the focus plane fixed. A device for controlling the movement of the image in the focus plane is coupled to whatever viewpoint shifting means is used and a scale is provided for indicating the range of the object when the control means is adjusted to the point at which the movement of the image is reduced to zero, 1

,A preferred form of a moving viewpoint range finder according to the invention consists of a support which may be either a frame or a hous- -ing with an eye-piece carried on the support. A

rotatable member is mounted on the front of the support, the term front not necessarily referring to any absolute orientation in space and the rotation being either complete in which case the member is a rotor or partial in which case the member is a pendulum. Two reflectors are carried by the rotatable member approximately parallel to one another and preferably rigid with respect to one another but either or both may be adjustable to alter the direction of reflection, i. e. of light deviation. The" outer one of the two reflectors is carried near the rim of the :rotatable slightly. An objective is carried either rigidlyy or. rotatably in the path of the light vand at the .proper distance from the focus plane of the eyepiece to form therein an image of the object; the

objective may be in front of the' outer reflector, between the reflectors or behind the inner reflector. Some means for controlling the amount of image shift during rotation of the rotatable member is provided in the light path and is coupled to rotate with the rotatable member. 'I'his control means may be a tilting mirror, a tilting block of glass, a sliding prism, a tilting prism, two

-mutually rotating prisms, a sliding lens element ;v

a tilting lens element, or other variable power wedge.

Furthermore additional wedge means are usually included in the' light path for various reacoincidence is only approximate. Theoretically the only absolute requirement is that when the instrument is set for infinity, the optic axis as it strikes the image plane coincide with the rotation axis at this point whether either 'or both have been reflected or otherwise deviated. The simplest embodiments of the invention have the rotation axis in approximate coincidence with a sons. With certain types ofl control means, zero deviation is available which corresponds to infinite `range. Since it is never necessary to measure beyond infinity, a suitable stop is sometimes ineluded to limit the range of the tilting mirror, tilting block or rotating wedges at this zero power position. On the other hand even with such control means it is usually preferable to employ their entire range, e. g. rotating prisms can be varied from maximum deviation in one direction to equal deviation in the opposite direction. In this case the additional wedge is used to compensate al1 of the deviation beyond infinity. This means that the additional wedge must exactly cancel the conaxis as lies the outer reflector.

ofcourse if one is interested only in ranges less than some finite maximum distance, the end of vthescale could be set for this finite range. but it is usually preferable to be able to check the instrument against infinity (the moon being a usefuliniinite" object for this purpose).

-Again the additional wedge may be made ad nJuStltble for' presetting the scale-for example against the infinite object.

Furthermore y`the additional wedge may be set to compensate for any errors in the system such as an improperly tipped reflector. These latter errors may cause deviation to any side of the rotation axis and hence the direction ofA compensation is not limited to the one used when presetting the scale. The latter direction is in the plane of symmetry ofthe rotating member which plane is the one containing. the rotation .axis and the optic axis between the reflectors.

lThe effective apex of the wedge system used for the control means is perpendicular to this plane of symmetry. The additional wedge means is not necessarily so oriented. The optic-.axis 0f the objective is also in this plane of symmetry yeven when deflected by the rotating reflectors, but after it strikes the image plane or even in front of this, the optic axis 'may be reflected to the eyepiece at any convenient angle.

large portion of the optic axis.

Specific forms of this new type of range finder are described in the following descriptionwhich corresponds to the accompanying drawings in which:

Fig. 1 illustrates the principle of the invention.

Fig. 1A shows the field of view through the instrument. a

Figs. 2, 3, 4, 5, and 6 are respectively a side elevation, a side elevation in cross section, a top view, a front view and a rear view of one embodiment of the invention.

Fig. '7 shows a sideelevation in cross section of partof a slightly different embodiment of the invention.`

Fis. s similarly shows'anotherv embodiment of.

the invention.

Fig. 9 similarly shows still a different embodiment of the invention.

Fig. 10 shows another embodiment of the lnvention.

Fig. 11 shows a simple adjustable wedge.

Fig. 12 shows a Pentagon prism.

Fig. 13 shows a pendulum type embodiment of the invention.

Fig. 14 shows a simplified embodiment of the invention. Fig. 15 shows a compact embodiment of the invention.

Fig. 16 showsan embodiment o1' the invention' server. The focus plane 23 may be considered` the focus plane either of the objective 2| or of the eye-piece 22. Mounted on this telescope 2 0 e is a rotating arm 25 which may be carriedA by a .Y invention such as where the objective shifts this rotor or simply act as a pendulum. This rotating arm 25 includes an outer reflector 20 and an inner reflector 21 by means of which light .from the object whose range is to be found is transmitted to the objective 2|. It is not absolutely necessary that the objective 2| be carried 'directly in front of the eye-piece 22, since it might conveniently be placed anywhere in the system such as in the rotating arm 25. between the reflectors 28 and 21 or even in front of the reflector 28.

For explanation of the theory of the invention, only points on the optic axis of the system. which is the axis of rotation 3| of the rotating arm 2l, are considered.' It will be noted that objects at infinite distance are brought to focus as indicated by rays 28 and 29 at a point 3 0 on the optic axis. On the other hand objects at nearer range as indicated by the rays 32 a'nd 33 are brought to focus at a' point 34 which rotates around' the axis as the rotating arm 35 is rotated.

Objects which are not on the Optic axis are embodiment l similarly brought to focus in the field of view, a complete inverted image being formed as in any telescope. Objects at infinite distanceform images which are held stationary and those at near-by range form images which shift with a circular motion relative to the optic axis. That is, the image of any particular object remains lnverted but moves with a circular motion unless Y n the object is at infinity. j

If, in this Fig. 1, one were to provide a light deviating means to bring the point 34 down to the optic axis (the point 30 being moved correspondingly to one side), the image of the object emitting the ray 32 would not shift as the rotating ann 25 is operated. The object at infinity would give a shifting image however when the image motion eliminator is so adjusted.

This light deviating means,o,r..more generally, this image motion eliminator or control means may consist of a simple arrangement for tipping either the mirror 26 or the mirror 21. Similarly it may consist of a sliding wedge, two rotating wedges, a laterally sliding lens, a variable power wedgemade up of adjacent plano concave and convex plano lenses, one of which is movable, or even a sphere-plano element as described" by Ort in U. S. Patent 2,191,027 or any of the other knownvariable power light deviating devices. The basis of the present invention lies in the use of an objective having a shifting viewpointrather than in the particular kind of light deviating device employed to stop the image motion. However the preferred forms of light deviating devices are described in detail in connection with other figures.

Ifa light deviating device is selected whose power ranges from zero to some finite value, the zero setting corresponds to infinity range in Fig. 1. If the light deviating device has finite power for both of its extreme values, it is advisable (even when one of the intermediate values is zero) to yinsert a compensating wedge or a limiting stop so that one of the limits in the setting of the device corresponds to infinity.

In Fig. 1A is shown the field of view when ranging a subject, a flag being selected as the example. In the general embodiment of the invention, the image 36 rotates without changing its orientation until the instrument is adjusted to eliminate this motion. If a fixed image such as shown by broken lines 31 is superpositioned on the field, as, for example, in the embodiment described in connection with Fig. 7, the image 36 rotates about this fixed image 31.

Figs. 2 to 6relate to the same embodiment of the invention and will be described simultaneously. In this embodiment an eye-piece 40 is positioned behind an erecting roof prism 4| for convenient viewing of the image formed in the focus plane of an objective 42. The objective is carried by a rotating member consisting of a tube 43 and -a rotor housing 44 in which is located a` prism having refiecting surfaces 45 and 46 to receive light from the object. Obviously, as the rotor is rotating, the viewpoint of the objective 42 is effectively shifted and in the focus plane of the objective, all images shift circularly except those of an object at some predetermined distance from the instrument.

The whole `rotating member is carried in bearings 41 and 48 and is securely mounted therein by suitable nuts and washers 49 and 56. The rotating arm orrotor inany of the embodiments may be hinged or detachable for convenient transport of the instrument. Also the periscoplc prism may be built of several similar units in cascade.'

In order to ascertain the range of an object,

the rotor 44 is rotated either by hand at a conveniently cut-away portion in the side of, the housing 14 or by a friction drive motor 16 mounted adjacent to one of these cut-away portions. A wedge 55, preferably achromatic, is provided slidably carried by a sleeve 56 in the tube 43. A pin 51 carried rigidly by this sleeve 56 extends through a slot 58 in the tube 43 and is fastened to a sliding collar 6U. Thisfcollar 60 and sleeve 56 may be moved longitudinally on the tube 43 and are pushed forward by a spring 59 against a ball-bearing 6| which is held in place by a control member 62. The control member 62 does not rotate with the tube 43, whereas the collar 60 does.- This control member 62 is carried on the frame of the range finder and is adjustable thereon by means of screw threads 63 and 64. Rotation of the drum 61 carries this control member 62 with it and moves a spiral scale 68 past an index 69 by means of which the distance of the object may be read off directly. Suitable dust covers 10 and 1I are provided for the adjustable control member.

In order to make a zero adjustment or, mor

correctly, an infinity adjustment of the scale 68, an adjustable wedge 12 mounted in collar 13 is provided on the front of the rotor 441. One form of said adjustable wedge is shown in detail in Fig. 11. If the reflecting surfaces 45 and 46 are absolutely parallel to one another the instrument is at infinity adjustment when the wedge 55 has no power or more exactly when the wedge 55 is exactly compensated by the wedge 12. Since it is useless to be able to measure objects beyond infinity@A the instrument is arranged so that one end oT'the scale reads infinity and the effect of the wedge 12 is exactly equal to Aand opposite to that of the wedge 55 when this wedge 515 is in the infinity position as indicated by the scale. For convenience in carrying, the frame 65 is provided with a handle in the form of a cut-away portion 66.

For maximum sensitivity the focal length of the objective 42 should be as long as possible; also l the image shift is quite sensitive to lens wobble and hence a preferable embodiment described below has the objective supported'independently of the rotor. In place ofthe compensating 'wedge being-as shown at 12, any form of variable wedge may be used; in certain embodimentsi'hesconi.- pensating wedge is arranged to be adjustable while the rotor is being rotated to permit presetting the scale means by checking on an object at a known distance. Whereas the control wedge need only deviate light in a direction parallel to the plane containing the optic axis between the reiiectors and the axis of rotation, the compensating wedge may be required to act in any plane through the axis of rotation and hence should'be either rotatable or made up of two variable wedges at right angles to compensate separately for each component of the infinity error. r

Figs. '1 and 8 show alternative forms of the rotating member and are intended to be cornpared with- Fig. 3. The, frame work, bearings, etc., are not shown in these Figs. 7 and 8.

ing surface 45 of Fig. 3 replaced by a surface 80 having an aperture therein through which the object may be viewed directly; To provide this aperture on the single prism, member containing the reflection surfaces 80 and 46, a small prism 8|, or more exactly a section 8| of a cylinder is cemented to the `axial region of the reflecting surface80. Light from the object passes through anaperture 82 in the front of the rotor 44 and through an aperture 84 in the prism 83 which replaces the wedge 55. In this embodiment, it is particularly necessary to have the wedge as near as possible to the reflecting surface 80. In fact, it may be preferable to use the rotating type ofwedge described in connection with Fig. 9 and an objective behind the wedgeI since in this case, the distance between the reflector and the wedge is small and does not change. However, for purposes of illustration the simple sliding wedge 83 is shown in Fig. 7. The other elements correspond, as numbered, to Fig. 3.

Similarly in Fig. 8, an inner reflecting surface 90 is provided the center portion of which is I i relative to theA rest of the wedge. Figs. 7 and 8 provide combinations of the present invention with the coincident type range finder as particularly described in my copending application, Serial No. 402,986, filed concurrently herewith. Aside from the utility for coincidence type range finding, the additional image serves as a reference plane for easier perception of movement.

In Fig. 9, there is shown another form of light deviating means and a `different arrangement for holding the objective 42. In this case the objective 42 is carried rigidly by a fixed sleeve |0I. Such an arrangement is preferable since tolerances for any motion of the objective are much smaller and more critical than for the other parts of the rotor and 'hence it is more important to hold this element rigid than to hold the rotor in proper alignment, although the latter is important. In this figure, the collar 60 of Fig. 3 is replaced by collar |02 carrying rack |03 and held in place by a spring |04 which presses against a collar |I2 fixed to the rotating tubel 43. As the collar |02 is moved longitudinally by means of the control member 62 and the ballbearing 6|, the rack |03 causes the pinion |05 to rotate and hence the bevel gear to rotate which in turn rotates the ring bevel gears ||0 and I. For accuracy an additional bevel gear |01 is provided opposite to the small drive gear |06. Rotating sleeves ||5, and the ring bevel gears ||0 and III carry wedges |08 land |09 which rotate equal amounts in opposite directions forming a rotating wedge type of light deviating means with the effective apex of the combination always perpendicular to the plane through the axis of rotation and the optic axis between the reflectors (i. e. the plane of the paper in the drawing). The rotating sleeves are carried by suitable receptacles ||3` rigidly fastened to the tube 43 by'studs |I4.

As the wedges |08 and |09 are rotated in opposite directions, they pass from a point in which they deviate the light a maximum amount in one direction to a point at which they deviate the light the maximum amount inthe other direction. As before, infinity is arranged at oneend of the scale and a compensating wedge such as the wedge 12 is provided somewhere in the system to give zero deviation for infinity setting. Of course, the compensating wedge may have any of the forms discussed above in connection with the light deviating means, such as adjustable reflectors in place of the reflectors 45 and 48 or sliding lenses, etc. ing means may be anywhere in the system, the one shown being simple and convenient.

Fig. utilizes the same form of light deviatlng means as shown in Fig. 9, but the operation of this control device is by means of an inner sleeve rather than an outer sleeve. In Fig. 10 the rotating wedges |08 and |09 with their bevel gears ||0 and are carried by a bevel gear set made up of the bevel ringgears ||0 and and bevel pinions |2| supported by spring members |22 in a. suitable sleeve |20. As before, the wedge |08 is carriedv by a rotating sleeve 5, but the Wedge |09 in this case is carried by a sleeve |24 having a gear |25 thereon. As'long as the sleeve |24 and the holding sleeve rotate together, there will be no relative rotation of the wedges |08 and |09 and since the holder |20 is carried rigidly by the tube 43, there will be no variation in light deviating power. However, the holder |20 is provided with a gear |23 having one tooth less (or one.

tooth more) than the gear |25 onthe sleeve |24. A pinion |26 engages both the gear |23 and the gear 25 and is carried by an innertube |21 in the tube 43. As the tube |21 is rotated, in the manner to` be described below, relative to the tube 43, the pinion |26 moves around the two gears |23 and |25 moving them1 relative to one another, one tooth for each complete circuit of the pinion |26. This provides the relative rotation ofthe sleeve |24 and the holder |20 and through the gears |2| provides an equal relative rotation of the sleeve ||5 in the opposite direction. I While the rotor and tube 43 are rotating, the tube |21 rotates therewith, except when some adjustment is required. A suitable driving mechanism'for the tube 43 is provided-by a'spur gear |29 engaging another spur gear |30 but which is integral with a bevel gear |3| driven by a bevel gear |32 mounted on a crank |33. The driving mechanism may be at the side but is shown on top of the instrument for clarity in the drawing. The inner tube |21 is similarly provided with a spur gear |20.

Through an idler |40, the gear |29 drives a spur gear |4| anda tubular shaft |43. The gear |28 similarly drives a spur gear |42 and its tubular shaft |44 directly. Due to the idler |40, theseA the proper number of teeth beingV provided, the

lgears |28 and |29 rotate with the same speed in the same direction and there is no relative movement of the wedges |08 and |09. However, when the knob 45 is rotated, there is a differential drive on the gears |46 and |41 providing a retarding of one relative to the other and hencev a change in speed of the rate of rotation of the Similarly the light deviatammasgears |29 and |29. As described in detail above this provides the necessary adjustment ofthe gear |59 engaging the spur pinion |55. This g drum is supported for free rotation by a tubular hub |59 on the tube 43 and is heldin place against the bearing 49 by a retaining ring |90. For convenience the scale |51 is mounted on translucent material and is backlighted by a lamp |59.

After a, setting has been made, further rotation of the knob |45 may be prevented by pressing a latch bolt into frictional contact with the surface |51 of the knob |45.` To do this the lever |62 pivoted at the point |53 is rotated and held in place by a spring |94 engaging notches |95 in the lever.

However, this is not the main purpose of the latch bolt l5! and lever |52. The main function oi this latch is utilized when the lever is pushed in the other direction so that the latch bolt 19| engages a recess |99 in the gear |42. This locks the gear |42 against further rotation so that turning the crank |33 must act to rotate the tube 43 relative to the now rigid inner tube |21. In-

cidentally, through the differential gear system in the knob |45, this knob rotates at the same time. For every rotation of the tube 43 relative to the inner tube |21', the gear |23 is advanced one notch relative to the gear which means there is a slight rotation of the wedges |09 and |09 relative to one another. Therefore, as the crank |39 is rotated, the instrument is in continuous adjustment and passes in cycles through the point of proper adjustment at which point the reading on the scale may be read oil'.

With this cyclic adjustment of the instrument, the scale |51 should read from infinity at one point to the near point at the opposite side of the scale and backto innity so that the scale is continuous and corresponds to the adjustment of the two wedges |08 and |09 continuously in opposite directions. That is, the scale is completely circular with the innity point and the near' point at opposite ends of a diameter about which diameter the sides of the scale are symmetrical. With the scale conveniently arranged so that it may be viewed with one eye while the other eye watches the motion of the image in the eye-piece, this cyclic arrangementl for continuous adjustment is particularly useful since several readings may be taken rapidly and chances for error thereby minimized. If desired the nal critical adjustment may be made directly with the automatic feature out of connection.

Fig. 11 shows a conveniently adjustable .compensating wedge useful on any kind of range finder or other instrument and particularly useful as wedge 12 shown in Figs. 3 to 10. A face plate or suppurt |10 is provided with a circular aperture or window |1|. Into this aperture fits a tube which is free to rotate and which has t-wo ring gears |14 and |15. Two wedges |12 lt onto the end of this tube and have as their mounts, ring gears |13, one of which has one tooth more and theother one tooth less than the gear |14. A pinion |15 carried by a freely rotating collar lilll engages all three gears |13 and |14. As this pinion |15 is vturned by the finger rotating it around the gear |14, the gears4 |13 turn 'slowly in opposite directions adjusting the powerof the two wedge combination altering the direction of its effective apex only very slightly.

Similarly a ring gear |11 having one tooth more or less than' the gear |19 is rigidly attached 4'to the face plate |10. A pinion |19 carried by a freely rotating collar |90 engages the gears |15 and |11 rotating the gear |15 slowly as it (|19) is rolled around the gear |11. 'I'his rotates both wedges together and adjusts the direction of the apex of the two wedge combination.

After the adjustments are'thus made, a cover Y plate |92 is clamped on by screws |93 and by means of a rubber gasket |19, the parts are clamped in place.

As is well known in range nder practicethe reiiecting surfaces may be Jreplaced by pentagon prisms such as |90 shown in Fig. 12, but ll prefer to use a single prism having parallel reflecting surfaces such as 45 and 45.

In Fig. 13, there is shown an embodiment of the invention in which the rotating arm 25 of Fig. 1 is replaced by a pendulum |86. It is not necessary to have complete rotation of the objective viewpoint, but obviously it is desirable to have this viewpoint follow an arcuate path such as that described by the rotating arm 25 or that described by the end of the pendulum |86 or at least to follow some repetitive path, to permit convenient arrangement of the light deviating means which must be coupled to the objective viewpoint changing apparatus and which must, when set for some particular reading, compensate exactly for the eilect of the shift along the path.

As pointed out above, it is preferable to have the objective of the system held rigidly. A con- Fig. 14. In this figure an eye-piece |90 is mounted in a support |9| and is slidable therein for ad.- justment to suit various observers. Light from `the object whose range is to be found is transmitted by reflectors |92 and |93 through an objective |94 to form an image at the focus plane of the eye-piece I9. to control any movement of the image while the reflectors |92 and |93 are rotated about the optic axis of the system. This wedge is adjustable longitudinally by a ring |95 engaging a ring |91 which may be moved by means of a link |99 and lever |99. A wing nut 200 is provided for holding the setting of this lever |99 and a scale 20| indicates the setting of the wedge |95, preferably in terms of the range being measured.

The objective |94 is rigidly supported in tube `205, butthe reflectors |92 and |93 and the wedge |95 are rotatably supported in bearings 204, 205,

and 206. The rotation is provided through gears 201 and 208 engaging long pinions 209, one of which is driven by a crank wheel 2|0. The gear 209 is rigidly attached to the tube 202 which carries the wedge |95 and as the wedge is adjusted the gear 209 slides longitudinally on the pinions 209. This arrangement'is particularly stable since wobble between the gears has only a small angular eil'ect at the centre of the large gear 208. A compensating wedge is not shown in this figure. but eimer the redentor |92 er the reflector |93 is made adjustable to provide the compensation necessary. In this Fig. 14, the reflectors |92 and |93 are formed in a Sprenger prism 2| so that one of the reflectors, (|92 in the figure) is` a roof surface and the central rays follow the path shown by broken lines 2|2 and 2|3 suffering a reection at the surface 2|4. Sprengerprism inverts the image and renders unnecessary an erecting eyepiece. It may be A wedge |95 is provided This used inverted and it may be substituted for the various forms shown in the other gures.

Fig. 15 shows a very compact arrangement and illustrates a practical method of permitting adjustment of the instrument in the field, i. e. while being used by the observer. In fact, in any of the previously described arrangements, the com- I pensating wedge should. preferably Inot be permanently ilxed, but should be an adjustable wedge of any of the types described so that the instrumentmay be focused onan infinitely distant object or on one at a known range, and the scaleand compensating wedge set so that the scale readings will be correct. In Fig. 15 light reaches an eye-piece 225 through an optical path which is 'folded back and forth. For 'conven- 12 222 is tilted or an additional ilxed wedge 245 is included.

Figs. 16 and 1'7 sho a particularly practical arrangement of my invention. For convenience' in showing, the objective 25| is mounted rotatable with the rotor 26| and the light deviating ience in showing, the optical path is drawn as mechanical details would diii'er somewhat from those shown, and the gears 225 and 225 would have to be offset. In Fig. 15 reflectors 222 and 222 are carried by the rotor 22| and are parallel to each other. Light from the reflector 222 passes through an objective 224\which is rigidly mounted on a support not shown. The rotor is driven by a gear 225 by means of a drive gear 225 and this gear 225 in turn drives the gears 221 and 225 to rotate the other portions of the optical system. After the light passes through the objective 224` it is reflected by prisms 225 through the remainder of the system to the eye-piece 225.

Any form of light deviating means may be provided, and in the arrangement shown, wedges 224 may be rotated equally in opposite directions by a gear 225. This gear 225 is driven by 'a pinion 222 engaging a rack 222 which is held by a spring 225 against the controlling member 220 which is adjustable by means of threads 22| and carries a scale which may be read against an index 2i5.

In each of the other arms of the system are respectively provided compensating wedges which are optically at right angles to each otherto compensate for any lack of alignment in the system and to compensate for any setting of the wedges 224 at the infinity position of the scale. For simplicity of explanation, sliding single wedges arev shown but other types may be used.

Since the means for adjusting the wedges 221 and 225 are similar, thearrangement thereof will be described only in connection with one of them. The wedge 221 is carried by a sliding sleeve 225 having a stud 24| rigidly fastened thereto and extending through a slot 245 in the rotating tube. This stud 24| rotates with the tube and slides in a ring recess 242 in a threaded sleeve 242 which engages the threads 244 fastened to the bearings. As the sleeve 242 is rotated, this ring recess 242 moves longitudinally on the tube carrying the wedge 221 with'it, and providing the The wedge 228 has sulcient' jective 25|.

means consisting of rotating wedge 255 is shown some distance behind the objective 25|', In practice, however, it is-preferable to have these elements arranged as .shown in Fig. 9 with the light deviating device in front of the objective and. th objective mounted rigidly.

In this connection it is pointed out that the sliding wedge type of light deviating device as shown in Figs. 2 to should be in the converging beam behind the objective, whereas therotating type of wedge may be either place, but preferably in front of the objective. In Figs. 16 and 17 an eye-piece 255 is positioned to view the focus` plane of the objective 25| mounted in the tube 25| to rotate in bearings' 252 with the rotor.252

having a frontwindow 254. A single prismof glass 253 comprises the outer and inner reflecting surfaces to receive light from the object whose range is to be found and to project it to the oblI'he light deviating meansv consists of two wedges 255 carried on bevel rings 255. The bevelpinion's engaging the bevel rings 256 are carried on pins 251 which in turn support bevel pinions 255 engaging a crown gear 259l mounted to rotate on the tube 25|. There will be novrelative rotation of the wedges 255 as long as the crown gear 259 rotates with the tube 25|.

On the crown gear 255 is mounted a spur gear 255 and the tube-25| is similarly provided with a spur gear 252. These two spur gears 258 and 253 engage a differential gear made up ofspur gears 210 and 212 respectively, an idler gear 211| being provided between the spur gear 252 and the spur gear212 to permit rotation of the gears 210 and 212 in opposite directions while the gears 252 and 252 rotate in the same direction.

This spur gear 252 is also used for driving the lmust rotate'in opposite directions with the same speed. lThis means that thegear 255 and the gear 252 rotate in the same direction with the same speed and hence there is no relative rotation of the prisms 255.` However, if the drum 211 is rotated causing the/ring gear 215 to rotate there is a diiference in the rotation of the disk gears 212 and 215 which provides r, relative rota tionv of the gear 255 and the gear 252. Through the pinions 255 and ring gears 255, this causes a relative rotation of the prisms 255 as required.

To provide the rotation of the drum 211 which carries a scale 218, there is provided an adjusting crank or handwheel 280 which for operation must be pressed' in against a light spring pressure provided by a spring 28| until a gear 282 13 below, is used. On the drum 211 there ls also provided a large crown gear 284 which engages a pinion 285 coupled to a spur gear 292. When a spindle 288 is pulled out by a knob 281 a pinion 288 is brought into engagement with the spur gear 292. To insure accurate positioning of the spindle 288 ring notches 289 and 290 are provided into Lwhich a click latch 29| is pressed by suitable spring pressure. A key 294 and keyway 293 coupling is provided between the spur gear 212 and the spindle 288 so that the spindle rotates with this gear 212. When the spindle 286 is in the position shown, the rotation of the rotor by gear 283 and the accompanying rotation of the gear 212 causes rotation of the spindle 286 which has no useful effect. However, when the knob 281 and spindle 288 are pulled out so that the latch 29| drops into the ring notch 290 and the gear 288 engages the spur gear 292, the rotation of this spindle also drivesthe drum 211 slowly. This provides the cyclic range measurement, discussed above. An additional eyepiece 295 is provided for Viewing the scale 218.`

By having the eye-pieces 250 and 295 spaced the interocular distance, theright eye may note the range as seen on the scale 218, when the left eye detects the cessation of image motion' on the object whose range is being found. For those who normally use the right eye for aiming and sighting, this arrangement is particularly suitable, because the left eye is equally adept at detecting motion or the absence thereof, whereas the right eye is most useful for reading the scale 218. The housing 298 is provided for the whole instrument and is preferably easily removable for any adjustment that may be necessary.

Any suitable wedge means adjustably mounted in the optical path may be used for presetting the scale as described in detail above. For this compensation, I prefer to use rotating WedgesV 300 similar to wedges 255 which can only rotate equally in opposite directions. The compensating wedge 300 is positioned between the objective 25| and the rotating wedges 255 and has the same form as the Wedges 255, and is adjustable only when the housing 298 is removed. In the arrangement shown, the Wedges 300 are arranged so that their effective wedge action is in the opposite direction to the effective wedge acl tion of the Wedges 255 and all adjustment at right angles thereto is provided by adjusting the Alternatively the wedges could be independently as` described in liig.V 18so that these wedges can correct for all types of errors.

These wedges 300 are adjusted by pinioris 30| and.,

a crown gear 302 and when the crown gear is'i Most of'the elements in this embodiment corresponding exactly to those shown in Fig. 16

and the same numbers have been used for corresponding parts. In order to get as much distance as possible between the lens, 308 in this case, and the focus plane, some of the parts are located slightly differently, but the correspondence between this figure and Fig. 16 is apparent as far as those elements having the same numy bers are concerned.

The differences comprise the fact that a stationary tube 305 is used to support the lens 308 rigidlyand both the measuring wedges 2:55 and the compensating wedges 301 are positioned in front of the lens 308. The compensating wedges 301 are mounted for independent rotation so that, within the range of deviating power available, this two-wedge combination may-have any desired power and act in any desired direction. Since they are identically mounted, only one need be described. The wedge 301 is supported by a crown ring gear 308 which is rotated by a bevel pinion 309..

another pinion 3|0 on the outer end. This outer of a ring spur gear 3|2 whichis freely rotatable on the tube 28|; ing one tooth more or less than the spur gear 3|2 is rigidly attached to the tube 28| both by screws and by the bushing for the pivot supporting the pinions 309 and 3|0. A pinion 3H engages both spur gears 3|2 and 3|3 and is carried by a housing 3|5 which normally rotates with the rotating tube 28|.

As long as this housing 3|5 rotates synchronously with the tube 28|, the pinion 3|4 remains in engagement with the same tooth of the gear 3|3 and there is no relative rotation of the gears 3|2 and 3|3. However, by means of a brake 3|8 on which pressure may be applied through a flnger key 3 |1, the housing 3|5 may be stopped temporarily. This causes the pinion 3|! to remain xed in space and the rolling of the pinion. on the gear 3|3 causes the gear 3|2 to rotate relatively thereto, and this causes rotation of the pinions 3|0 and 309. Thus while the rotor tube 28| is rotated by means of crank 261, the wedges 301 are adjusted simply by braking the housings 3|5 by nger pressure on thekeys 3|1. It will be noted that the adjustment of the wedges 301 is very slow relative to the rotation of the tube 28| since it requires a complete revolution of the4 out turning the wedge 301 through 360 degrees. .The keys 3|1 are purposely placed inside the housing 298 since it is not necessary to adjust these compensating wedges 301 except once in a long while. Since the wedges arejndependently adjustable it is possible'to have any desired -deviating power and to have the deviation in any desired radial direction. In practice brake controls are mounted convenient for the right hand but for clarity are shown on the lett side` of the instrument.

Figs. 19 and 20 show a simplified embodiment of the invention wherein a single element is used both as the objective and as the light deviating means. In these figures an eyepiece 320 receives light twice reflected in a prism 32| which rotates with a rotor and rotating tube 322. In the front end of this tube 322 is mounted a diaphragm 323 for the objective. The objective consists of a convex plano element, but could be more complicated with a plano spheric element as one of its components. For this embodiment, it is necessary that the optical 'system include a plano` convex element, or a plano concave element, but this element need not be isolated as shown but may be either one component vof a more complicated objective or may be combined with a neutralizing plano spheric element of equal but oppo- The pivot for the pinion 309 ex-` tends through the rotating tube 28| and carries A similar spur gear 3|3 hav- 15 site power to give a variable wedge of known form.

In the embodiment shown the lens 324 is carried by a mount 325 having arms 326 extending backwards and pivoted to rotate about pivots 321. These pivots 321 are on a line perpendicular to the optic axis of the element at the center of curvature of its spheric surface, which is convex in the embodiment shown. The pivots 321 are supported by the tube 322 and extend through slots 328 in an inner sleeve 330 which carries studs 329. These studs 329 engage sloping surfaces of the arms 326 and sliding of the tube 330 inside the tube 322 causes the arms 326 to move up and down against the action of a spring 335. The tube 330 is held in place by a spring 33| and presses against ball-bearings 332 engaging a control member 333 which is screwed onto part ofl the frame 334. As the control member 333 is screwed down, the tube 330 moves forward inside the tube 322 causing the lens 324 to move downward against the pressure of the spring 335. This causes all light entering the front of the objective 324 to be bent downward since the rear surface of the element 324 acts as the rear surface of a prism, whereas the front surface has an unchanged effect on the incident beam. As pointed out above, this element 324 may be used isolated as shown or as one component of a more comlimited 'to these specic structures but is of the scope of the appended claimsi What I claim and desire to secure by Letters Patent of the United States is: y

1. The method of range finding an object which comprises forming an image, of the object by an objective, shifting `the effective viewpoint of the objective along a repetitive path to shift said image relative to the opticv axis of the objective without rotation of the image, arresting the motion of the image relative to the optic axis while continuing the shifting of the viewpoint, by adjustingan image motion eliminator and noting .ne adjustment.

2. A method according to claim 1 in which the shifting of the viewpoint is in an arcuate path giving an arcuate motion to the imagev 3. A method according to claimi in which the shifting of the viewpoint isin a circular path giving a circular motion to the image.

4. A method of range finding an object which comprises forming an image lof the object by an objective, shifting the effective viewpoint of the objective along'a repetitive path to shift said image relative to the optic axis of the objective without rotation of the image, adjusting an image motion eliminator while continuing the shifting of the viewpoint and noting the adjustment when the motion of the image relative to the optic axis is arrested.v

5. The method according to claim 4 in which the steps of adjusting and shifting of the viewpoint are coupled.

6. The method according -to claim 4 in which the adjusting is cyclic and the stops of adjusting .my invention. I wish to point out that it is not lthe rotatable member,

which the objective is between the '7. A range finder comprising an objective for forming in a focus plane an image of the object whose range is to be found, means for shifting the e'ective viewpoint of the objective along an arcu'ate path whilekeeping the focus planeiixed,v

adjustablev means coupled to said shifting means `for controlling the movement of said, image in the focus plane and means operated by the controlling means for indicating the range of the object when said controlling means is adjusted to the point at which said movement is zero.

8. A range finder comprising a support, an eyepiece carried by the support, an -objective for forming in the focus plane of the eyepiece an image of the object whose range is tobe found, a rotatable member mounted on the front of the support to rotate at least partially about a rotation axis which substantially coincides with at least part of the optic axis of the objective, two reflectors carried by the rotatable member approximately parallel to one another and positioned to receive light from the object on one of the reflectors which is an outer one, to one side of the rotation axis and to reflect it inward to the other reflector which isA an inner one on the rotation axis and which reflects the light approximately along the rotation axis and to the focus plane, the objective being inthe path of said light, and having a viewpoint which shifts as the` rotatable member is rotated, .adjustable control means operated in synchronism withv the movement of the rotatable member for controlling the apparent amount of the corresponding movement of the image in the focus plane and scale means for indicating the adjustment of'said control means when the image movement during the rotation of the rotatable member is reduced to zero.

9. A' range nder according to claim 8 in which the objective is between the focus plane and the inner reilector.

l0. A range finder according to which the objective is mounted to rotate with 1l. A range iinder according to focus plane and the inner reect'or and there.l

rotatable member is rotating.

l2. A range nder according -to claim v8 in which the two reflectors are formed in a single prism, having an entrance and exit surfaces substantially normal to the light beam therethrough.

13. A range `finder according to claim 8 -in which adjustable means are lmounted in the light path rotatable with the rotating member for presetting the scale means.

14.'A range finder according to claim'8 inpendulum pivoted at the other end of the sup-` port. a reilector carried at the lower end of the g pendulum to receive light from the object whose and shifting of the viewpoint are coupled whererange is to be found and to reilect it along the pendulum; an inner reflector carried by the pendulum at its pivot to receive the reected light claim 8 inv.

claim 8 in. x

is `*included means for holding the objective rigid while, they and again to reflect it along the axis of rotation of the pendulum to the eyepiece, an objective positioned in the path of said light for focusing in the focus plane of the eyepiece an image of said object, variable light deviating means carried by the pendulum also in said path for controlling the amount of the image movement during swinging of the pendulum, means carried by the support for adjusting Athe light deviating means and scale means coupled to the adjusting means for indicating the object range when said movement is reduced to zero.

17. A range finder comprising a support, an eyepiece carried by the support, a rotor rotatably mounted on the front of the support, a reflecting surface carried near the rim of the rotor to receive light from the object Whose range is to be found and to reect it toward the axis of rotation of the rotor, an inner reflecting Asurface carried by the rotor on its axis to receive the reected light and again to reect it along the axis,the eyepiece being positioned to receive the light, an objective in the path of said light for focusing in the image plane of the eyepiece an image of said object, means rotatable with the rotor and also in said path for controlling the amount of limage movement during rotor rotation, means on the support for adjusting the control means, and scale means coupled to the adjusting means for indicating the adjustment when said image movement is zero.

18. A range finder according to claim 17 in which the control means is a wedge system for deecting said image laterally, which" wedge system is adjustable to vary the amount of the deection.

19. A range nder according to claim 17 in which the objective is rigidly supported by the support.

v20. A range finder according to claim 17 in which the objective is between the-focus plane and the control means which is a variable power optical wedge system positioned to receive the iight reflected from the inner reflector.`

21. A range under according to claim 17 in which the control means consists of a variable deviating power wedge system carried by the rotor between the inner reector and the focus plane and mounted with its eective apex perpendicular to the plane containing the rotation axis and the optic axis between the two reflectors.

22. A range finder according' to claim 17 in which the control means consists of two substantially identical wedges rotated with the rotor and mounted for adjustment by relative rotation equally in. opposite directions from the eective apex of the two wedge combination which effective apex is maintained perpendicular to the plane containing the rotation axis and the optic axis between the two reflectors.

23. A range nder according to claim 17 in which the control means consists of a variable power light deviating means including a plano spheric lens element mounted rotatable about a line through the center of curvature of its spheri surface.

2a. A range nder comprising a support, an eyepiece carried by the support, a rotor rotatably mounted on the front of the support, a reflecting surface carried near therim of the rotor to receive light from the object whose range is to be found and to reect it toward the axis of rotation of the rotor, an inner reflecting surface carried by the rotor on its axis to receive the reected light, and again to reect it along the axis, an objective rigidly supported by the support to receive the multiply reflected light and to focus in the focus plane of the eyepiece an image of said object, two wedges mounted rotatable with the rotor in front of the objective with the effective apex of the two wedge combination perpendicular to the plane containing the axis of rotation and the optic axis between the reflectors, adjusting means on the support for rotating the two wedges laterally and equally in opposite directions to vary their total light deviating power and to control the amount of image movement during rotation, scale means for indicating the 'adjustment ln terms of object'range when said image movement is reduced to zero and additioihal compensating wedge means in the light Dit 25. A range finder according to claim 24 in which the additional wedge means has the power which cancels all deviation between the light from the object and the light through the objective when the two-wedge combination is set for maximumdeflection to one side of the axis, said one side being the one on which lies the rim reector, whereby this setting of the wedge.

combination corresponds to infinity range.

26. A range finder according to claim 24 in which the additional wedge means is adjustable for presetting the scale means.

27.A range finder according to claim 24 in which the additional wedge means is adjustable and means are carried on the support for adjusting this wedge means while the rotor is rotating. Y 28. A range finder according to claim 24 in which the additional wedge means has the power which cancels all deviation between the light from the object and the light through the objective when the two `wedge combination is set for maximum deection to one side of the axis, said one sidebeing the one on which lies the rim reector and in which the scale means includes a completely circular scale with the infinity point and the near point at opposite ends of a diameter about which the sides of the scale are symmetrical i 29. A range under according to claim 24 in which there is included means for adjusting the wedge means synchronously with and slowly relative to the rotation of the rotor.

30, A range jnder according to cla-im 21 in Vwhich the adjusting means for rotating the rotating the wedges in proportion to the relative rotation of the rotor and concentric member, a differential gear with opposite sides geared respectively to the rotor and the concentric member to rotate equally in opposite directions when the rotor and concentric member rotate synchronously, a rotatable support for the end gears of the diiferential and nmeans for rotating the rotatable support to give relative rotation of the rotor and the concentric member, the scale means being coupled to the last mentioned rotating means.

31. A range finder comprising a support, an eyepiece carried by the support, a rotor rotatably mounted on the front of the support, a reflecting surface carried near the rim of the rotor to receive light from the object whose range is to be found and to reflect it toward the axis of rotation o the rotor, an inner reecting surface carried by the rotor on its axis to receive the reilected light, and again4 to reflect it along the axis, an objective carried by the rotor to focus in 20 y the support for moving the lens element about said line and scale means for indicating the ad- Y justment of the lens element when the image movement during rotor rotation is reduced to BENJAMm E. LU'BosHFz.l 

